Iraqi insurgents said Tuesday they killed a Bulgarian hostage and would put a second hostage to death in 24 hours, Al-Jazeera television reported.
However, the report could not be validated and the police chief in the town of Mosul said Wednesday that both hostages are still alive.
The group, Tawhid and Jihad, had said it would kill the two truck drivers if the United States didn't withdraw its troops by last Saturday.
Headed by Jordanian Abu Musab al-Zarqawi, the group has claimed responsibility for the beheadings of American Nicholas Berg and South Korean Kim Sun-il. Washington believes al-Zarqawi is linked to al-Qaeda leader Osama bin Laden.
Al-Jazeera broadcast a video of masked men standing behind Bulgarian hostage Georgi Lazov, 30. The network said the videotape contained the killing, but it was too graphic to broadcast.
Bulgaria identified the second hostage as Ivaylo Kepov. The two men were kidnapped around June 29.
Bulgaria has about 480 soldiers stationed in Iraq and has sent diplomats to the country to try to free the hostages.
Another Iraqi insurgent group holding an Egyptian hostage demanded the Saudi company he works for pull out of Iraq within 72 hours.
The fate of a Filipino hostage remains unclear after the Philippines issued a statement Monday saying they would pull out of Iraq. However, the Philippine government then imposed a media blackout, refusing to provide any further details.
Some reports Wednesday said the Filipino hostage had been released.
The group Khaled Bin Al-Walid Squadrons, part of the Islamic Army of Iraq, has threatened to kill Angelo dela Cruz, 46, unless the Philippines pulls its 51-member peacekeeping force from Iraq by July 20.
President Gloria Macapagal Arroyo has said the country would pull it troops by Aug. 20, the date the force's mandate was to expire.